1. Field of the Invention
The present invention relates to a detonator (or blasting cap) system with high precision delay, and more particularly, to such a detonator system for mining, quarrying, and construction where the sequencing of detonation of output charges is important to achieve predetermined results.
2. Description of the Related Art
Several designs for detonator systems have been designed in the past. None of them, however, includes the detection of the different characteristics (pressure/shock, light emission, and heat) of an incoming non-electric impulse with a redundancy in order to avoid false detonations. The prior art systems utilizing non-electrical impulses only use the shock characteristic typically to activate a piezoelectric generator. The present invention detects the additional characteristics of a non-electrical impulse, such as the light emitted, its pressure, and its spark. The present invention does not depend exclusively on the generation of electricity by a transducer from the mechanical force of an incoming impulse. By providing a redundant system for accurately delaying the detonation, undesirable results are avoided that could be caused by erratic currents, magnetic fields, movements, and other mechanical effects from the area.
The shock tube is known in the art and it is made out of a plastic hose or conduit with an explosive mass in its interior. Examples of these explosive masses are PETN, hexogens, octogens, HNS, or a mixture of pyrotechnic material. The objective in the non-electrical impulse systems is to deliver the initial detonation with accurate delays and without requiring complicated electrical connections for the transmission line. To obtain the electrical energy, most systems rely on the energy transmitted through a shock tube, but this approach limits the circuitry that can be utilized as well as the length of the time it can be used without exhausting the power acquired through a piezoelectric generator. The latter limitation also affects the magnitude of the delays that can be achieved. If a battery element is included, the energy stored in the battery should be kept below a threshold amount to avoid accidental explosions, as documented in U.S. Pat. No. 5,435,248 (Rode et al), col. 4, lines 3-6. Many times it takes days from the time a system is deployed for it to be activated at a subsequent time.
Applicant believes that the closest reference corresponds to U.S. Pat. No. 5,435,248 issued to Rode et al in 1998 for an extended range digital delay detonator. However, it differs from the present invention because the extended range digital delay detonator, while using an incoming non-electrical impulse, fails to provide for the necessary redundancy to avoid accidental malfunctioning of the circuit. The present invention provides for a number of different and independent circuits that analyze the input impulse for its different characteristics. Additionally, the present invention's circuitry is not active at all times. Rather, it is active only at predetermined times periods, thus saving energy. The sensors are enabled over predetermined windows or periods of time. Also, the voltage potential is raised to levels that will trigger the detonator charge at a time just prior to the detonation, reducing the risk of accidental detonation at other times.
The disclosures in U.S. Pat. Nos. 5,435,248 and 5,377,592, to the extent that they use a capacitor only to store energy for the pertinent electronic circuits, have power limitations that can result in the failure of their systems to operate. The selection of a combination of low power batteries to permit a system to last for days while keeping it rated value below a threshold that could accidentally activate the primary explosive charge in the electric detonator is a problem in the industry. The present invention resolves this problem, and others, by selecting a battery low enough power to minimize accidental activation, management of independent circuitry that is kept in ultra low power consumption mode, and providing sampling windows to reduce the duty cycle consumption further until the detection of an input impulse in the shock tube.
Other documents describing the closest subject matter provide for a number of more or less complicated features that fail to solve the problem in an efficient and economical way. None of these patents suggest the novel features of the present invention.